The aim of the present study was to evaluate the effects of a 16-week progressive high-intensity strength training (HIST) program on peripheral markers of bone turnover (bone Gla protein, BGP; bone alkaline phosphatase, B-AP; N-terminal propeptide of type I procollagen, PINP; C-terminal cross-linked telopeptide of type I collagen, ICTP) in healthy, elderly men over 65 yr of age. Thirty healthy men (aged 65-81 yr), performing light to moderate daily physical activity, were randomly divided into two groups. Group 1 (no.=16) followed a supervised 16-week progressive HIST program, while subjects of group 2 (no.=14), used as controls, were requested to maintain their habitual level of physical activity for 16 weeks. HIST program consisted of 6 different sets of exercise (2 involving the major muscle groups of the lower limb and 4 involving those of the upper limb). Three sessions/ week, during which 10 repetitions of each exercise set were completed, were performed. Lower limb exercises shifted from 50 to 80% of the one maximal repetition (1 MR) during the first month of the protocol and were thereafter maintained at an intensity of 80% 1 MR throughout the training. Upper limb exercises shifted from 40 to 65% of 1 MR with a similar pattern. All sessions were preceded by 15 min of cycloergometer exercise at 50% of maximal oxygen uptake and by a warm-up of 15 repetitions at 20% of 1 MR of each exercise set. The HIST program did not significantly change BGP (mean SE, before: 15.6 +/- 1.2 microg/l vs after: 16.0 +/- 1.2 microg/l, NS) and PINP levels (before: 44.6 +/- 6.7 microg/l vs after: 43.1 +/- 6.0 microg/l, NS). On the contrary, serum B-AP significantly increased (before: 50.2 +/- 6.1 IU/l vs after: 62.3 +/- 7.0 lU/l, p<0.001) and serum ICTP slightly reduced (before: 4.0 +/- 0.3 microg/l vs after: 3.8 +/- 0.3 microg/l, p<0.05). When bone turnover was expressed as the ratio between bone formation to bone resorption (B-AP/ICTP ratio), a significant improvement in this ratio was found in all subjects of group 1 (before: 12.9 +/- 1.3 lU/microg vs after: 17.3 +/- 1.5 IU/microg, p<0.0001), while no significant changes were observed in Group 2. No significant changes of IGF-I levels were observed after the HIST program (before: 94.9 +/- 9.4 microg/l vs after: 89.9 +/- 9.7 microg/l). No significant changes of BGP, PINP, B-AP, ICTP, B-AP-ICTP ratio and IGF-I levels were observed in controls (group 2) during the 16 weeks of observation. Although the positive effects of a progressive HIST program on B-AP levels and B-AP-ICTP ratio seem promising, the support of bone mass measurement and the determination of other bone markers are requested to better identify exercise protocol (duration, intensity) for elderly people.